I must admit a bit of surprise that so many "blue" states are relaxing NPIs (Non-Pharmaceutical Interventions) for the pandemic at a time when new case rates, while falling, are still quite high. Is this all too soon? Too late?
What Do the Models Predict?
Most of us don't have the mathematical background to critique the various pandemic models, but let's look a little closer at one of them. The Institute for Health Metrics and Evaluation (IHME) is an independent population health research organization based at the University of Washington. IHME was founded in 2007 and is one of my favorite sources for data and forecasting during the pandemic.
Let's look at their most recent data compiled February 17. This is a link I'd really encourage you to explore because as you will see the graphs are interactive. Although I've set the link to open for the view of the United States, you can search anywhere.
It's important to look at several different outcomes, especially in the omicron era, to get an accurate picture. We have lots of variability in healthcare seeking and testing behavior, plus as my wife reminded me most of those rapid home test results don't get reported to any public health authority. However, hospitalization rates are a reasonable assessment of what's going on plus focus on an outcome that we care about most. Here's a screen shot of IHME's current projection for hospital bed use in the US.
This is certainly encouraging, though projections will depend on what future variants have in store for us.
Variant Alphabet Soup
Writing in the BMJ, journalist Elisabeth Mahase reminds us that the World Health Organization first designated omicron a variant of concern on November 26, 2021. A lot has happened in the last 3 months. In Pango-speak (Phylogenetic Assignment of Named Global Outbreak lineages, a software tool) it is designated B.1.1.529.1, now BA.1 for short. It accounts for >90% of cases globally currently, including in the US. BA.1 seems to have increased transmissibility but lower severity, although as we've seen it can still stretch our healthcare resources beyond capacity. It exhibits immune escape in terms of infection, though vaccine and natural immunity still provide good to excellent protection against severe disease, depending on individual circumstances.
The subvariant BA.2 (B.1.1.529.2) is a bit in the spotlight now, comprising a few percent of US cases as we hold our breath to see if it precipitates another infection wave. BA.2 certainly has a faster replication rate than BA.1 and likely is more transmissible. Although cases have been reported throughout the world, it's still a bit early to judge relative severity.
BA.3 is much less common so far. Its spike protein mutations aren't that different from BA.1 and BA.2; much remains to be learned about its ability to spread and cause severe disease.
NPI relaxation across the US leads us into a new era of the pandemic. We'll see what this experiment reveals in the coming months.